A known dry cleaning machine includes a solvent circulating path with the inlet at the bottom of the outer tub, which contains a rotating drum, and the outlet at the top of the outer tub. In the solvent circulating path, a pump and a filter are provided. In such a dry cleaning machine, the solvent is circulated through the circulating path by the pump and is cleaned by the filter while the laundry is washed Thus the solvent is not discharged from the dry cleaning machine and is repeatedly used.
Petroleum solvent, for example, shows the best washing performance when it is around 25° C., and the washing efficiency decreases at higher or lower temperatures. Since the petroleum solvent has a rather low firing point, it bears safety problems when the temperature rises. In the above structure using the solvent circulating system, the temperature of the solvent changes due to the heat transfer from the surroundings, and the temperature rises due to the heat transfer from the pump and functions with the circulating path. In conventional dry cleaning machines, a cooler or a heater is provided in the circulating path, and they are controlled to maintain the temperature of the solvent at around 25° C.
In normal conventional dry cleaning machines, besides the cooler for cooling the solvent, another cooler is provided for condensing, liquefying and recirculating the solvent evaporated from the laundry while it is dried. Thus, generally, two coolers are provided in conventional dry cleaning machines.
The applicant of the present invention proposed a new type of dry cleaning machine, which is disclosed in the Published Unexamined Japanese Patent Application No. 2002-119797, etc. In the dry cleaning machine, a solvent cooler with a solvent pipe is placed between the heater for heating the air, which is supplied to the outer tub while drying, and a drying cooler for condensing the solvent gas. In this structure, the air cooled by the drying cooler exchanges heat with the solvent pipe, so that the solvent is cooled. Thus, in this structure, the cooler for cooling the solvent is no more necessary, which lowers the cost of the machine.
The dry cleaning machine works without problem when the ambient temperature is rather low. When, however, the ambient temperature is very high, in summer for example, the temperature of the solvent tends to increase due to the heat transfer from the surroundings. In such a case, the cooling performance of the coolers is not enough even if the cooler is operated at its largest capacity. The temperature of the solvent may, in some cases, exceed 30° C.
The present invention addresses the problem, and one of the primary objectives of the present invention is to provide a dry cleaning machine in which the solvent can be maintained at the adequately low temperature even when the conditions are severe, for example the ambient temperature is high.